U.S. patent number 7,921,678 [Application Number 12/143,442] was granted by the patent office on 2011-04-12 for compressible resilient fabric, devices, and methods.
This patent grant is currently assigned to Atex Technologies, Inc.. Invention is credited to Brian L. McMurray, Martin Monestere, Jr., Stephanie Booz Norris.
United States Patent |
7,921,678 |
Norris , et al. |
April 12, 2011 |
Compressible resilient fabric, devices, and methods
Abstract
A compressible resilient fabric can include a ground layer of
knitted yarn, and a loop layer comprising a plurality of loops of
yarn, each loop having a point knit into the ground layer. The
fabric can be compressible from an non-compressed configuration, in
which each loop has an apex extending substantially perpendicularly
outward from the ground layer, into a compressed configuration, in
which each loop is collapsed onto the ground layer. The fabric can
further be resilient so as to substantially resume the
non-compressed configuration when compression is relieved. The loop
layer yarn can include a multifilament yarn having a high denier
per filament ratio. The ground layer yarn can include a yarn
shrinkable substantially more than the loop layer yarn. The loops
can be densely knit so as to support the extension of the loops
outward from the ground layer.
Inventors: |
Norris; Stephanie Booz (Rocky
Point, NC), Monestere, Jr.; Martin (Hollywood, SC),
McMurray; Brian L. (Pinehurst, NC) |
Assignee: |
Atex Technologies, Inc.
(Pinebluff, NC)
|
Family
ID: |
39971070 |
Appl.
No.: |
12/143,442 |
Filed: |
June 20, 2008 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20080319521 A1 |
Dec 25, 2008 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
60936405 |
Jun 20, 2007 |
|
|
|
|
Current U.S.
Class: |
66/195 |
Current CPC
Class: |
D04B
21/205 (20130101); A61F 2/07 (20130101); D04B
21/04 (20130101); D10B 2509/06 (20130101); Y10T
442/45 (20150401); A61F 2/06 (20130101) |
Current International
Class: |
D04B
1/22 (20060101) |
Field of
Search: |
;66/202,191,194
;623/1.49-1.54 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
08768655.6 |
|
Feb 2010 |
|
EP |
|
08768655.6 |
|
Mar 2010 |
|
EP |
|
WO 02/28314 |
|
Apr 2002 |
|
WO |
|
Other References
International Search Report, PCT/US02/007684, mailed Jan. 28, 2009.
cited by other .
Written Opinion of the International Searching Authority,
PCT/US02/007684, mailed Jan. 28, 2009. cited by other.
|
Primary Examiner: Worrell; Danny
Attorney, Agent or Firm: Boggs IP Law, LLC
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims benefit of U.S. Provisional Patent App. No.
60/936,405, filed Jun. 20, 2007, which is incorporated by reference
herein in its entirety.
Claims
What is claimed is:
1. A fabric, comprising: a ground layer of knitted yarn; and a loop
layer comprising a plurality of loops of yarn, each loop having a
point knit into the ground layer, wherein the fabric is
compressible from a non-compressed configuration, in which each
loop has an apex extending substantially perpendicularly outward
from the ground layer, into a compressed configuration comprising a
thickness of about 0.004-0.008 inches and in which each loop is
collapsed onto the ground layer, and wherein the fabric is
resilient so as to substantially resume the non-compressed
configuration by returning the loops to approximately an original,
non-compressed height when compression is relieved.
2. The fabric of claim 1, wherein the ground layer yarn comprises a
yarn shrinkable substantially more than the loop layer yarn.
3. The fabric of claim 1, wherein the ground layer yarn comprises a
yarn having a higher shrinkability than the loop layer yarn.
4. The fabric of claim 1, wherein the loop layer further comprises
two loops in every four courses of the ground layer.
5. The fabric of claim 1, wherein the loop layer further comprises
between about 600 and about 750 loops per square inch of the
fabric.
6. The fabric of claim 1, wherein each loop further comprises a
substantially uniform height in the non-compressed
configuration.
7. The fabric of claim 1, wherein the fabric further comprises a
thickness of about 1-5 mm in the non-compressed configuration.
8. The fabric of claim 1, wherein at least the loop yarn further
comprises a polyester yarn.
9. The fabric of claim 1, wherein the loop layer yarn comprises a
multifilament yarn having 5-20 denier per filament.
10. The fabric of claim 1, wherein the ground layer comprises a
porosity sufficient to allow collapse of each loop onto the ground
layer.
11. A fabric, comprising: a ground layer of knitted yarn; and a
loop layer comprising a plurality of loops of multifilament yarn
having a total denier of about 60-70, each loop having a point knit
into the ground layer, wherein the fabric is compressible from a
non-compressed configuration, in which each loop has an apex
extending substantially perpendicularly outward from the ground
layer, into a compressed configuration comprising a thickness of
about 0.008 inches and in which each loop is collapsed onto the
ground layer, and wherein the fabric is resilient so as to
substantially resume the non-compressed configuration having a
thickness between about 1 mm and about 2 mm by returning the loops
to approximately an original, non-compressed height when
compression is relieved.
Description
FIELD OF THE INVENTION
The present invention relates to compressible resilient fabric,
devices including a compressible resilient fabric, and methods for
making and/or using a compressible resilient fabric and/or device
having a compressible resilient fabric.
BACKGROUND
Medical devices such as vascular and endovascular grafts and
stent-grafts can include fabric components that function to promote
sealing of the device to the lumen or structure in which it is
implanted. Insertion of such devices and fabric components into
target sites can require that the fabric be compressed and
collapsed so as to be placed inside a delivery catheter or cannula.
When such a device having a fabric component is inserted to a
target site and the delivery catheter is removed, at least the
fabric component is often expected to rebound to approximately its
original shape, structure, and dimensions. Regaining its original
shape, structure, and dimensions is important to achieve an
adequate seal between the exterior of the device and the lumen or
structure in which it is implanted. This is critical because any
gaps or voids between the device and the implant site can prevent a
reliable seal, which can lead to complications and/or device
failure. The ability of such a fabric component to regain its
original shape, structure, and dimensions after being compressed
and implanted can often depend on the fabric having sufficient
resiliency.
In some applications, medical devices comprising fabric and
designed for insertion into vessels or ducts may be stored in a
compressed, or collapsed, configuration for extended periods, for
example, a number of months, before use. When stored in sterile
packaging, such devices are secluded from exposure to ambient air.
In such devices stored for prolonged periods in a compressed state
and without exposure to ambient air, recovery of fabric to its
original shape and dimensions can be adversely affected. In
addition, some implantable medical devices can be stored in fluid
media over various periods of time. Fabric components of such
medical devices can absorb fluid media in which they are packaged
and stored. When medical device fabric absorbs fluid media, the
fabric may be lose some resiliency for regaining its original shape
and dimensions when deployed.
Thus, there is a need for a fabric that can be compressed for ease
of delivery to an implant site and that has sufficient resiliency
to regain its original shape, structure, and dimensions when
implanted. There is a need for such a fabric that can avoid the
loss of performance characteristics during storage prior to
use.
SUMMARY
The present invention can include embodiments of a compressible
resilient fabric, devices including a compressible resilient
fabric, and methods for making and/or using a fabric and/or device
having a compressible resilient fabric.
In an illustrative embodiment, a compressible resilient fabric can
include a ground layer of knitted yarn, and a loop layer comprising
a plurality of loops of yarn, each loop having a point knit into
the ground layer. The fabric can be compressible from a
non-compressed configuration, in which each loop has an apex
extending substantially perpendicularly outward from the ground
layer, into a compressed configuration, in which each loop is
collapsed onto the ground layer. The fabric can be resilient so as
to substantially resume the non-compressed configuration when
compression is relieved.
In some embodiments, the loop layer yarn can comprise a
multifilament yarn having a high denier per filament ratio. For
example, the loop layer yarn can comprise a multifilament yarn
having 5-20 denier per filament. In some embodiments, the loop
layer yarn can comprise a total denier of 60-70. In some
embodiments, the ground layer yarn can comprise a yarn shrinkable
substantially more than the loop layer yarn. For example, the
ground layer yarn may comprise a yarn shrinkable about 40-60%, and
the loop layer yarn can comprise a yarn shrinkable about 7-8%. In
some embodiments, the loops can be densely knit so as to support
the extension of the loops outward from the ground layer.
Some embodiments of the present invention can include a device
comprising a substantially tubular inner member, and an
intraluminal sealing member attachable to an exterior of the inner
member. The sealing member can include a ground layer of knitted
yarn and a loop layer comprising a plurality of loops of yarn, each
loop having a point knit into the ground layer. The sealing member
can be compressible from an non-compressed configuration, in which
each loop has an apex extending substantially perpendicularly and
radially outward from the ground layer, into a compressed
configuration, in which each loop is collapsed onto the ground
layer. The sealing member can further be resilient so as to
substantially resume the non-compressed configuration when
compression is relieved, for example, after the device is implanted
into a lumen in a human or animal body. The intraluminal sealing
member can be adapted to promote sealing between the inner member
and a lumen wall. In some embodiments, the inner member can
comprise a stent.
Some embodiments of the present invention can include a system
and/or kit. Such a system and/or kit can include a compressible
resilient fabric and/or devices including a compressible resilient
fabric as described herein.
Some embodiments of the present invention can include a method of
making a compressible resilient fabric and/or devices including a
compressible resilient fabric. Such a method can include knitting a
ground layer of yarn and a loop layer comprising a plurality of
loops of yarn, each loop having a point knit into the ground layer.
The method can further include washing the fabric in about 90
degree C. water. The method can further include drying the fabric
at about 60-65 degrees C., which further shrinks the fabric. In the
fabric and/or device made by such a method, the fabric can be
compressible from a non-compressed configuration, in which each
loop has an apex extending substantially perpendicularly outward
from the ground layer, into a compressed configuration, in which
each loop is collapsed onto the ground layer. The fabric can
further be resilient so as to substantially resume the
non-compressed configuration when compression is relieved.
Features of a fabric, device, system, kit, and/or method of the
present invention may be accomplished singularly, or in
combination, in one or more of the embodiments of the present
invention. As will be realized by those of skill in the art, many
different embodiments of a fabric, device, system, kit, and/or
method according to the present invention are possible. Additional
uses, advantages, and features of the invention are set forth in
the illustrative embodiments discussed in the detailed description
herein and will become more apparent to those skilled in the art
upon examination of the following.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic side view of a compressible resilient
fabric in a non-compressed configuration in an embodiment of the
present invention.
FIG. 2 is a diagrammatic side view of the compressible resilient
fabric shown in FIG. 1, showing the loops compressed into the
ground layer in a compressed configuration.
FIG. 3 is a diagrammatic cross-sectional view of a tubular-shaped
compressible resilient fabric in a non-compressed configuration in
an embodiment of the present invention.
FIG. 4 is a diagrammatic perspective view of a partially cut-away
intraluminal sealing member on the exterior of a stent in an
embodiment of a device of the present invention.
FIG. 5 is a view of a knitting stitch diagram of one four-course
repeat for a compressible resilient fabric showing two loops in
four courses in an embodiment of the present invention.
DETAILED DESCRIPTION
For the purposes of this specification, unless otherwise indicated,
all numbers expressing quantities, conditions, and so forth used in
the specification are to be understood as being modified in all
instances by the term "about." Accordingly, unless indicated to the
contrary, the numerical parameters set forth in the following
specification are approximations that can vary depending upon the
desired properties sought to be obtained by the embodiments
described herein. At the very least, and not as an attempt to limit
the application of the doctrine of equivalents to the scope of the
claims, each numerical parameter should at least be construed in
light of the number of reported significant digits and by applying
ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting
forth the broad scope of the described embodiments are
approximations, the numerical values set forth in the specific
examples are reported as precisely as possible. Any numerical
value, however, inherently contains certain errors necessarily
resulting from the standard deviation found in their respective
testing measurements. Moreover, all ranges disclosed herein are to
be understood to encompass any and all subranges subsumed therein.
For example, a stated range of "1 to 10" should be considered to
include any and all subranges between (and inclusive of) the
minimum value of 1 and the maximum value of 10; that is, all
subranges beginning with a minimum value of 1 or more, e.g. 1 to
6.1, and ending with a maximum value of 10 or less, for example,
5.5 to 10. Additionally, any reference referred to as being
"incorporated herein" is to be understood as being incorporated in
its entirety.
For the purposes of this specification, terms such as "forward,"
"rearward," "front," "back," "right," "left," "upwardly,"
"downwardly," and the like are words of convenience and are not to
be construed as limiting terms. As used in this specification and
the appended claims, the singular forms "a," "an," and "the"
include plural referents unless the context clearly dictates
otherwise. Thus, for example, the term "a loop" is intended to mean
a single loop or more than one loop.
The present invention can include embodiments of a compressible
resilient fabric, devices including a compressible resilient
fabric, and methods for making and/or using a fabric and/or device
comprising a compressible resilient fabric. Some embodiments of
compressible resilient fabrics, devices, and methods according to
the present invention may be useful for medical applications, for
example, a stent comprising an intraluminal sealing member.
For purposes herein, "compressible" is defined as the ability of
the fabric or intraluminal sealing member to be compressed from a
relatively larger, expanded configuration to a relatively smaller,
compressed configuration. For example, the fabric and/or
intraluminal sealing member can be compressed from its original
non-compressed configuration to the compressed configuration. In
some embodiments, the entire dimension of the fabric along its
length and width can be compressed. For purposes herein,
"resilient" is defined as the ability of the fabric or intraluminal
sealing member to recover from the compressed configuration to
substantially its original shape, structure, and dimensions as in
the non-compressed configuration.
In an illustrative embodiment, as shown in FIGS. 1-3, a
compressible resilient fabric 10 can include a ground layer 20 of
knitted yarn, and a loop layer 30 comprising a plurality of loops
32 of yarn 31, each loop 32 having a point 33 knit into the ground
layer 20. The fabric 10 can be compressible from a non-compressed
configuration 40, in which each loop 32 has an apex 34 extending
substantially perpendicularly outward 42 from the ground layer 20,
into a compressed configuration 41, in which each loop 32 is
collapsed onto the ground layer 20. The fabric 10 can be
sufficiently resilient so as to substantially resume the
non-compressed configuration 40 when compression is relieved.
In some embodiments, the loop layer yarn 31 can comprise a
multifilament yarn 31 having a high denier per filament ratio. For
example, the loop layer yarn 31 can comprise a multifilament yarn
31 having 5-20 denier per filament. In some embodiments, the loop
layer yarn can comprise a total denier of 60-70.
In some embodiments, the ground layer yarn can comprise a yarn
substantially more shrinkable than the loop layer yarn 31. For
example, the ground layer yarn may comprise a yarn shrinkable about
40-60%, and the loop layer yarn 31 can comprise a yarn 31
shrinkable about 7-8%.
In some embodiments, the loops 32 can be densely knit so as to
support the extension of the loops 32 outward from the ground layer
20. For example, in certain embodiments, the loop layer 30 can
include two loops 32 in every four courses of the ground layer 20.
In particular embodiments, the loop layer 30 can include between
about 600 and about 750 loops 32 per square inch of the fabric 10.
In some embodiments, each loop 32 can have a substantially uniform
height 43 in the non-compressed configuration 40.
In the non-compressed configuration 40, some embodiments of the
fabric 10 can have a thickness 43 of about 1-5 mm. In the
compressed configuration 41, some embodiments of the fabric 10 can
have a thickness 44 of about 0.004-0.008 inches. Thus, some
embodiments of the fabric 10 can be compressed into a very thin
profile for insertion to a target site in a location in a body, and
recover to substantially its original non-compressed configuration
40 when positioned in the location and compression is relieved.
In some embodiments, the loops 32 can be constructed as "unitary"
with the ground layer 20. A "unitary" construction means that loops
32 are knit in a set repeat pattern so as to provide a uniform
density. With a uniform density, gaps and voids in the knit pattern
can be avoided. In some embodiments, the loops 32 can be
constructed as "integral" with the ground layer 20. An "integral"
construction means that the loops 32 are knit simultaneously with
and into the ground layer 20. In some embodiments, the apex 34 of
the loops 32 can be substantially erect, or perpendicular 42 to the
face side, or technical face, of the ground layer 20 of the fabric
10.
The fabric 10 may be compressed from its original non-compressed
configuration 40 into the smaller, compressed configuration 41 by
employing, for example, a mechanical crimping apparatus (not shown)
designed for reducing the overall size of an intraluminal medical
device 50. Once crimped to the smaller size, the fabric 10 (and
device) can be loaded into a delivery catheter. When a compressive
pressure, such as the wall of a delivery catheter, is removed from
the compressible resilient fabric 10 and/or medical device 50
comprising the fabric 10, the fabric 10 can recover from the
compressed configuration 41 to substantially its original
non-compressed, or expanded, configuration 40. Such recovery to
substantially the original non-compressed configuration 40 can
include return of the loops 32 to approximately the original,
non-compressed loop, or pile, height 43 and other dimensions and
shape.
Such self-recovery can be facilitated by various aspects of the
present invention, as described herein. For example, in some
embodiments, resilient recovery of the loops 32 to the
non-compressed configuration 40, including their non-compressed
loop height 43, can be provided at least in part by loop yarns 31
having higher denier per filament and relatively fewer filaments of
yarn 31. In some embodiments, resilient recovery of the loops 32 to
the non-compressed configuration 40 can be provided at least in
part by the ground layer yarns having substantially higher
shrinkage capacity than the loop layer yarns 31, which can cause
the loops 32 to be tightly held in the ground layer 20 when the
fabric 10 is heated. In some embodiments, resilient recovery of the
loops 32 to the non-compressed configuration 40 can be provided at
least in part by each loop 32 being integrally knit into the ground
layer 20, thereby providing tightly held loops 32 that tend to
extend in an upright manner 42 away from the ground layer 20. In
some embodiments, resilient recovery of the loops 32 to the
non-compressed configuration 40 can be provided at least in part by
the loops 32 being densely knit into the ground layer 20 so as to
enhance the stability of the loops 32 in their outwardly extended
position 42. In some embodiments, resilient recovery of the loops
32 to the non-compressed configuration 40 can be provided at least
in part by thermoset memory of the fabric 10, as described
herein.
The "point" 33 of the loop 32 is the portion of the loop 32 that is
integrally knit into the ground layer 20. The "apex" 34 of the loop
32 is the portion opposite the point 33 of the loop 32 that extends
outwardly away from the ground layer 20.
Due to the resilient recovery property of embodiments of the fabric
10 of the present invention, each loop 32 can stand up by itself
from its point 33 knitted to the ground layer 20. Accordingly, in
the non-compressed configuration 40, the dense, extended loops 32
in the loop layer 30 of the fabric 10 can provide a consistent
height 43 and contour. In this manner, the loop layer 30 can have a
consistent contact with the interior wall of a vessel, duct, or
other anatomical structure along the length and width of the fabric
10. Such consistent contact with an adjacent vessel, duct, or other
anatomical structure can enhance clotting and prevention of fluid
flow between the exterior of an implanted device 50 such as the
stent 53 and the vessel, duct, or other anatomical structure.
In some embodiments, the loop layer yarn 31 can comprise a
multifilament yarn 31 having a high denier per filament ratio.
"Multifilament" is defined as a manufactured fiber yarn composed of
many fine filaments. Multifilament yarn 31 is desirable in some
embodiments of the present invention due to the greater surface
area exposed to a target location provided by multiple filaments in
the yarn 31. In applications in which the fabric 10 is utilized in
vascular implantation, for example, the multifilament loop yarn 31
can promote enhanced cellular ingrowth and encapsulation to promote
clotting and fixation of the fabric 10 to a vessel wall. Lower
denier filament yarns, such as those used in conventional medical
textiles, provide increased surface area but generally fail to
exhibit sufficient recovery or resiliency from compression (due to
limited memory retention) to provide optimal sealing between an
implantable device and an adjacent anatomical structure, such as a
vessel wall.
The stability and resilience of the fabric 10, and in particular
the loops 32, can be related to the denier per filament ratio (dpf)
in the multifilament loop yarn 31. "Denier" is defined as the
weight per unit length of yarn. Denier is numerically equal to the
weight, in grams, of 9,000 meters length of yarn. The lower the
denier, the lighter and finer the yarn. The higher the denier, the
heavier and more coarse the yarn. "Denier per filament" (dpf) is
defined as the size of each filament in a multifilament yarn equal
to the total yarn denier divided by the number of filaments. The
lower the dpf ratio, the harder it is for the loops 32 to spring
back to their original configuration 40. Conversely, the higher the
dpf ratio, the easier it is for the loops 32 to recover to the
non-compressed configuration 40. Conventional medical device
fabrics may comprise yarn having a total denier of about 150 and
about 96 filaments, for a relatively low denier per filament (dpf)
ratio of about 1.56.
In some embodiments of the compressible resilient fabric 10 of the
present invention, the loop layer yarn 31 can have a total denier
of about 60-70 denier and a relatively high denier per filament
(dpf) ratio of about 5-20. That is, the denier per filament ratio
in loop layer yarn 31 in the compressible resilient fabric 10 can
be about 5-20 dpf, or about three to ten times greater, and the
number of filaments can be about 40-50% less, than in conventional
medical device fabric. In certain embodiments, the total denier for
the loop yarn 31 in the compressible resilient fabric 10 can be
less than about 60, for example, as low as about 10-15 denier,
depending on the particular application for the fabric 10.
In addition to providing more stable loops 32 having greater
resiliency, the higher denier per filament yarn 31 in the fabric 10
can provide loops 32 that are more compressible than conventional
fabric having lower denier per filament yarn. It was discovered in
experimentation that two layers of multifilament loop yarn 31
having a total denier of about 60-70 allows a compressed fabric
thickness 45 of about 0.008 inches. This degree of compressibility
was found to be sufficient for utilization in medical device
applications. In addition, multifilament loop yarn 31 having a
total denier of about 60-70 was found to provide sufficient
resilience for the loops 32 to recover substantially their
non-compressed configuration 40 having a thickness between about 1
mm and about 2 mm of when compression was relieved.
Fluid media may have an impact on resiliency and/or uniformity of
resiliency of the fabric 10. Yarns having a relatively lower denier
per filament ratio tend to absorb more fluid from fluid media in
which they are packaged than yarns having a relatively high denier
per filament ratio. Absorption of fluid from packaging media can
cause the yarns to increase in volume, resulting in less resiliency
when a compressive force is released from the fabric 10. Therefore,
some embodiments of the compressible resilient fabric 10 of the
present invention comprising high denier per filament yarn 31 may
absorb less fluid from packaging media, and the resiliency of such
fabric 10 may thus be less adversely affected by fluid media, than
conventional medical device fabrics.
In some embodiments, yarn in the ground layer 20 can have heat
shrinkage rates, or shrinkability, up to 40% to 60% of the length
and width of the unprocessed ground layer 20. Such high rates of
shrinkage in the yarn in the ground layer 20 can cause the courses
and wales in the ground layer 20 to move closer together. In some
embodiments, the yarns in the ground layer 20 can be under a higher
tension than the yarns 31 in the loop layer 30. A tighter ground
layer 20 can provide more densely positioned loops 32, thereby
helping the loops 32 stand up and extend outwardly from the ground
layer 20. As a result, the dense positioning of the loops 32 can
help stabilize the loops 32. In this manner, the loops 32 can be
securely positioned for consistent functionality after the
compressible resilient fabric 10 is implanted within a patient and
the fabric 10 is expanded to the non-compressed configuration 40.
That is, when the compressive force is removed from the fabric 10,
the loops 32 can recover, or resiliently reposition, to
approximately their original, non-compressed height 43, which can
be a substantially uniform height 43. Such a recoverable,
substantially uniform loop layer height 43 can be particularly
useful in medical applications in which a device may not completely
conform to the contours of an anatomical structure in which it is
implanted.
As described herein, the fabric 10 can be washed, dried, and heated
during fabrication in order to shrink the high shrinkage ground
layer yarn so as to cause the loop layer yarns 31 to stand up more
effectively. A higher tension ground layer 20 can cause the loop
points 33 to be tightly packed and the loop apices 34 to be at the
greatest possible distance from the surface of the ground layer 20,
thereby providing maximum loop height 43.
In particular embodiments, the loop yarn 31 can be a synthetic
yarn, for example, a polyester yarn, with a heat shrinkage rate of
between about 5% and about 8%. Maintaining the heat shrinkage rate
of the loop yarn 31 in such a narrow range can provide shrinkage
control of the loops 32 so that the compressibility, resilience,
and other properties of the finished fabric 10 can be more
consistent and predictable. Alternatively, a polyester yarn having
a heat shrinkage rate in a broader range, such as between about 2%
and about 10%, may be utilized for the loop yarn 31. When using
such a yarn having a broader range of heat shrinkage rate, finish
processing can be varied to control the compressibility,
resilience, and other properties of the finished fabric.
Embodiments of the compressible resilient fabric 10 and/or device
50 can comprise various materials. Many synthetic materials can be
utilized to promote thrombogenesis when implanted as an
intraluminal sealing device 50. For example, nylon and/or
polyolefins can serve as thrombogenic material(s) useful in the
intraluminal sealing device 50. In certain embodiments, polyester
may be utilized for the ground layer 20 and/or the loop layer 30
yarn(s) 31. In particular embodiments, different polyester yarns
may be used in the ground layer 20 and loop layer 30. Polyester is
known to be well-adapted for promoting tissue in-growth in and
around the yarn.
In alternative embodiments, the compressible resilient fabric 10
can be fabricated with dissolvable materials. Such dissolvable
materials can include, for example, polyglycolic acid (PGA) and/or
ploylactide acid (PLA). Depending on the particular application,
the compressible resilient fabric 10 can be fabricated with
dissolvable materials alone or in combination with non-dissolvable
materials, such as polyester.
In the compressed configuration 41, the fabric 10 can have a
thickness 44 in the range of about 0.004-0.008 inches. Such a thin
compressed configuration 41 can allow the fabric 10 to be easily
inserted into a delivery catheter along with an intraluminal
medical device, such as the device 50. The compressed thickness 44
of the fabric 10 can be affected by various factors, including, for
example, the type of yarn, the porosity of the ground layer 20, and
the density and height 43 of the loop layer 30.
For example, in the non-compressed, or expanded, configuration 40,
the ground layer 20 can be very thin, for example, in the range of
about 0.05-0.1 mm in height. The loops 32 can have a height 43 from
the ground layer 20 of about 1-3 mm. In certain embodiments, the
loop height 43 can be greater than 3 mm, depending on the size of
the implantable device (for example the device 50) to which it is
attached relative to the size and configuration of the vessel into
which the device 50 is implanted. For example, if the design of the
implantable device 50, such as the stent 53, is inserted into a
particularly tortuous vessel and leaves a 4-5 mm gap between the
exterior surface of the device 50 and the wall of the vessel into
which it is implanted, the height 43 of the loops 32 can be 4-5
mm.
The compressibility and/or resiliency in the compressible resilient
fabric 10 needed for particular applications can vary. For example,
in some clinical situations, compressibility may be of greater
concern in order to compress the fabric 10 or device 50 comprising
such fabric 10 into a small enough delivery catheter to reach a
target implant site. In other situations, resiliency may be a more
important consideration for fuller recovery of the loops 32 to
their non-compressed height 43 so as to provide a tighter seal
between the device 50 and the vessel wall. That is, in some
embodiments of the present invention, the fabric 10 can be
constructed to provide an optimized balance between a sufficiently
low number of loops 32 and/or height/density for adequate
compressibility and a sufficiently high number of loops 32 and/or
height/density for resilient recovery. Such balanced loop density
and height 43 can be optimized for particular applications, for
example, a heart valve or for a stent-graft for an aneurysm.
The compressibility and recovery of embodiments of the fabric 10
from the compressed configuration 41 to its substantially original
non-compressed configuration 40 can be affected by a variety of
factors. Such factors can include the type of yarn, the denier per
filament of yarn, the fabric construction, and the method of
fabrication, among others. For example, in some embodiments, the
ground layer 20 can have a porosity that can provide some space
into which the loops 32 can be compressed. In some embodiments, the
loops 32 can be held tightly and/or densely packed on the ground
layer 20. In some embodiments, the loops 32 can be sufficiently
thin to allow packing in a compressed state and/or sufficiently
thick to allow sealing with clots. In particular embodiments, the
yarn in the ground layer 20 can comprise about two-thirds of the
fabric volume, and the yarn 31 in the loops 32 can comprise about
one-third of the fabric volume.
Some embodiments of the present invention can include a device 50,
as shown in FIG. 4, comprising a substantially tubular inner member
51, and an intraluminal sealing member 52 attachable to the
exterior of the inner member 51. In some embodiments, the inner
member 51 can comprise an implantable medical device, for example,
a stent 53. FIG. 3 illustrates a cross-section of the fabric 10 (or
sealing member 52) in a tubular configuration, as may be applied to
the inner member 51. The sealing member 52, or fabric 10, may be
attached to the tubular inner member 51 using various techniques.
For example, the sealing member 52, or fabric 10, may be attached
to the tubular inner member 51 with an adhesive material, by
stitching the sealing member 52, or fabric 10, to the inner member
51, or by other methods.
The sealing member 52 can include the ground layer 20 of knitted
yarn and a loop layer 30 comprising a plurality of loops 32 of yarn
31, each loop 32 having a point 33 knit into the ground layer 20.
The sealing member 52 can be compressible from a non-compressed
configuration 40, in which each loop 32 has an apex 34 extending
substantially perpendicularly and radially outward 42 from the
ground layer 20, into a compressed configuration 41, in which each
loop 32 is collapsed onto and/or into the ground layer 20. The
sealing member 52 can be resilient so as to substantially resume
the non-compressed configuration 40 when compression is relieved,
for example, after the device 50 is implanted into a lumen in a
human or animal body. The intraluminal sealing member 52 can be
adapted to promote sealing between the inner member 52 and a lumen
wall.
As shown in FIGS. 3 and 4, the implantable device 50 and the inner
member 51 can be tubular in shape. Such tubular embodiments can be
utilized in cardiovascular applications, such as with a heart valve
or stent-graft. In such applications, the intraluminal sealing
member 52 can be formed, wrapped, or attached about the radially
expanding inner member 51. In this manner, when the device 50 is
implanted in a target location, flow of blood between the exterior
of the device 50 and the wall of the vessel can be restricted
and/or prevented. When the device 50 is radially expanded, there
can be gaps and/or voids between the implanted device 50 and the
vessel wall because the flexibility of the device 50 may not
completely conform to the contours of the vessel. The intraluminal
sealing member 52 can fill those gaps and/or voids. Accordingly,
the sealing member 51, and/or fabric 10, can function as an in vivo
sealant or gasket for the expandable medical device 50. In certain
embodiments, the loops 32 can comprise a thrombogenic material,
such as polyester, that can further enhance clotting by the sealing
member 52, or fabric 10. In addition, the intraluminal sealing
member 52 can serve as a frictional retention mechanism to help
secure the implanted device 50 to the target location in the
body.
In some embodiments of such a device 50, the loop layer yarn 31 can
comprise a high denier per filament multifilament yarn 31. For
example, the multifilament yarn 31 in the device 50 can have 5-20
denier per filament. In some embodiments, the loop layer yarn can
comprise a total denier of 60-70. The high denier per filament yarn
31 can enhance the ability of the loops 32 to stand upright so as
to extend substantially perpendicularly outward 42 from the ground
layer 20. Such structural support within the loops 32 can provide
enhanced stability to the loops 32 to maintain their upright
positioning 42. In certain embodiments, each loop 32 can have a
substantially uniform height 43 in the non-compressed configuration
40. As a result, the loop layer 30 of the intraluminal sealing
member 52 can provide a consistent contact, and thus a reliable
seal, between the underlying tubular inner member 51 and the wall
of a lumen into which it is implanted.
In some embodiments, the ground layer yarn of the intraluminal
sealing member 52 can comprise a yarn that is substantially more
shrinkable than the loop layer yarn 31. For example, the ground
layer 20 may comprise a yarn shrinkable about 40-60%, and the loop
layer 30 may comprise a yarn 31 shrinkable about 5-8%. The loop
yarn 31 and/or the ground yarn can comprise various yarns. A
particularly useful type of yarn in either or both layers 20, 30,
respectively, is a polyester yarn. The polyester yarn can be
different in each of the ground and loop layers 20, 30,
respectively.
In some embodiments of such a device, the loops in the intraluminal
sealing member can be densely knit to further enhance the upright
stability of the loop layer. For example, the loop layer can
include two loops knit in every four courses of the ground layer.
In certain embodiments, the loop layer can include between about
600 and 750 loops per square inch of the fabric.
In some embodiments of such a device 50, the intraluminal sealing
member 52 can be compressed from the non-compressed configuration
40 to the compressed configuration 41. In the non-compressed
configuration 40, some embodiments of the sealing member 52 can
have a thickness of about 1-5 mm. In the compressed configuration
41, some embodiments of the sealing member 52 can have a thickness
of about 0.004-0.008 inches.
In some embodiments of the present invention, the multifilament
loops 32 can promote clot formation within the loops 32. A typical
clotting cascade can occur in which blood clots form first on the
inside of the loops 32 and then progressively outwardly until a
clot forms a solid connection between the fabric 10 and/or sealing
member 52 and the adjacent anatomical structure, such as a vessel
wall. In this way, the clot facilitated by the loop structure and
size can help secure the fabric 10 and/or device 50 in place and
prevent blood flow around the outside of the device 50. The height
of the loops 32 can vary, depending on the underlying device 50,
the target location for implantation, and the degree of loop
compressibility desired. A greater height of the loops 32 provides
a larger surface area for clot formation and can minimize
dislodgement of the forming clots. An optimal loop height 43 can
allow promotion of clot formation while allowing sufficient
compressibility of the loops 32.
In some embodiments, movement and positioning of the compressible
resilient fabric 10 and/or device 50 can be monitored
fluoroscopically or under CT visualization. For example, the
compressible resilient fabric 10 can include radiopaque material
such that positioning and expansion of the device 50 and the
attached fabric 10 can be monitored. Radiopaque is defined as being
opaque to radiation and especially x-rays. In certain embodiments,
a plurality of radiographic markers (not shown) can be in
communication with predetermined portions of the compressible
resilient fabric 10 and/or implantable device 50 so that when the
device 50 moves, movement and positioning of the markers--and the
fabric 10 and/or device 50 in communication therewith--can be
visualized.
Embodiments of the compressible resilient fabric 10, device 50,
system, kit, and method as described herein can be utilized in
medical applications, including, for example, in vascular and
endovascular implants such as stents, stent-grafts, and heart
valves. Some embodiments may be applicable for use in various other
types of anatomical structures and locations, for example, in
shunts between organs and/or in gastrointestinal, pulmonary,
neurological, and/or other structures and locations of a human or
animal body.
Embodiments of the compressible resilient fabric 10 and/or device
50 can have advantages over conventional fabrics and devices. For
example, one advantage is that the fabric 10 and/or sealing member
52 can be sufficiently compressible for inserting into a target
location and sufficiently resilient to recover to substantially its
non-compressed configuration 40 when in the target location and the
compression is relieved. As a result, the fabric 10 and/or sealing
member 52 are adapted to promote sealing between the fabric 10
and/or sealing member 52 and an adjacent anatomical structure, such
as a lumen wall. In certain embodiments, the compressible resilient
fabric 10 and/or device 50 can provide frictional contact between
the fabric 10 or device 50 and the adjacent anatomical structure.
Such a frictional contact can help prevent blood flow around the
fabric 10 and/or device 50 and provide a surface for clot formation
to further secure the fabric 10 and/or device 50 in the desired
implant position.
Another advantage of some embodiments of the compressible resilient
fabric 10 and/or device 50 is that the loops 32 can have sufficient
stability in the perpendicularly extended (upright) position 42
relative to the ground layer 20 to provide a uniform loop height
43, and thereby consistent contact with an adjacent anatomical
structure. Loop stability can be advantageously provided by various
aspects of embodiments of the present invention. For example, the
loops 32 can be stabilized in the outwardly extended position 42 by
each loop 32 being integrally knit into the ground layer 20, by
knitting the loops 32 closely together in a dense pattern, by high
denier per filament yarn 31 in the loops 32, and by the ground yarn
having a high shrinkage capacity that when shrunk causes the loops
32 to become more tightly packed.
Another advantage of some embodiments of the compressible resilient
fabric 10 and/or device 50 is that loops comprising high denier per
filament yarn can retain resiliency when stored in fluid media.
Some embodiments of the present invention can include a system
and/or kit. Such a system and/or kit can include a compressible
resilient fabric 10 and/or devices 50 including a compressible
resilient fabric 10 as described herein. For example, some
embodiments of such a system and/or kit can include the fabric 10
and/or intraluminal sealing member 52 comprising a ground layer 20
of knitted yarn, and a loop layer 30 comprising a plurality of
loops 32 of yarn 31, each loop 32 having a point 33 knit into the
ground layer 20. The fabric 10 and/or intraluminal sealing member
52 can be compressible from an non-compressed configuration 40, in
which each loop 32 has an apex 34 extending substantially
perpendicularly outward 42 from the ground layer 20, into the
compressed configuration 41, in which each loop 32 is collapsed
onto the ground layer 20. The fabric 10 can be resilient so as to
substantially resume the non-compressed configuration 40 when
compression is relieved.
The loops 32 in embodiments of the fabric 10 and/or intraluminal
sealing member 52 can be stabilized in the outwardly extended
position 42 by various means, including by each loop 32 being
integrally knit into the ground layer 20, by knitting the loops 32
closely together in a dense pattern, by high denier per filament
yarn 31 in the loops 32, and by the ground yarn having a high
shrinkage capacity that when shrunk causes the loops 32 to become
more tightly packed.
The system and/or kit may further comprise additional components,
for example, a delivery catheter for a device that includes the
fabric 10 and/or intraluminal sealing member 52.
Some embodiments of the present invention can include a method of
making a compressible resilient fabric 10 and/or devices 50
including the compressible resilient fabric 10 as described herein.
For example, one such a method can include knitting the ground
layer 20 of yarn and the loop layer 30 comprising a plurality of
loops 32 of yarn 31, each loop 32 having a point 33 knit into the
ground layer 20. In the fabric 20 and/or device 50 made by such a
method, the fabric 10 can be compressible from the non-compressed
configuration 40, in which each loop 32 has an apex 34 extending
substantially perpendicularly outward 42 from the ground layer 20,
into the compressed configuration 41, in which each loop 32 is
collapsed onto the ground layer 20. The fabric 10 can further be
resilient so as to substantially resume the non-compressed
configuration 40 when compression is relieved. In some embodiments
of a method, the loop layer 30 can be knit with a multifilament
yarn 31 having 5-20 denier per filament and a total denier of
60-70. A high denier per filament yarn can increase the
extensibility and stability of loop positioning.
Embodiments of the compressible resilient fabric 10 and/or
intraluminal sealing member 52 of the present invention can be made
utilizing warp knitting techniques, for example, on a double-bar
raschel knitting machine. As used herein, "warp knitting" is
defined as a method of knitting fabric out of one or more sets of
yarn prepared as warps on beams. The yarns are fed through one or
more guide bars to knitting needles that form the yarns into
interlaced loops 32. The guide bars move the yarns around the
needles and from needle to needle to create the warp knit fabric.
In warp knitting, there is simultaneous yarn-feeding and
loop-forming action occurring at every needle in the guide bar
during the knitting cycle. All needles in the needle bar are
simultaneously lapped by separate guide bars. A "warp knit fabric"
is a knit fabric in which the yarns generally run lengthwise but in
a zigzag patterns, which forms loops 32 in two or more wales.
In one alternative warp knitting technique to form the high pile
fabric 10, a "dummy needle" can be used to fill a needle space on a
knitting machine when no needle is required for the pattern. In
another alternative warp knitting technique, yarn ends can be
looped around a pole to help form a loop 32 into a particular size.
Use of a "pole" or pile sinker can be helpful for knitting
relatively larger loops 32.
Warp knitting can be advantageous for making the compressible
resilient fabric 10 and/or intraluminal sealing member 52 in that
warp knitting decreases the risk of the fabric 10 or sealing member
52 from fraying and from unraveling when cut. Warp knitting
provides a manufacturing process that can result in consistent
quality of knitted products.
In some embodiments of the compressible resilient fabric 10 and/or
intraluminal sealing member 52, the loops 32 can be integrally knit
with the ground layer 20 utilizing a stitch design that ensures the
points 33 of the loops 32 are held tightly to the ground layer 20.
Such tight loop layer 30--ground layer 20 knitting can help the
loops 32 stand upright 42 away from the ground layer 20 surface,
thereby contributing to the resilience of the loops 32.
FIG. 5 shows a knitting stitch diagram of one four-course repeat
for one exemplary embodiment of the compressible resilient fabric
10. The 3-2-1-0 designation in FIG. 5 represents spaces between
needles along the direction of the wales in the fabric 10. Courses
1-4 are indicated along the left hand side of the diagram. In this
knitting pattern, four guide bars (bars 1-4) alternate between two
needle beds. While bars 3 and 4 knit in their respective courses,
bars 1 and 2 each knit once in every four-course repeat. Thus, bars
1 and 2 produce open stitch loops 32 in alternating courses,
providing two loops 32 in every four course repeat. The stitch
notation in FIG. 5 designates the path of the yarn on each bar
between the needles. For example, the yarn on bar 1 travels in
course 1 starting in space 1 and forms loop ending in space 0;
stays in space 0 in courses 2 and 3; and then moves to space 1 in
course 4. Since the yarn stays in the same space (space 0) in
courses 2 and 3, an open stitch loop 32 is formed.
In some embodiments, selected guide bars from which the ground
layer 20 is knit can be tightly spaced so as to knit the ground
layer 20 more tightly to create a more densely packed loop layer
30. In some embodiments of a method, the loop layer 30 can be knit
having between about 600 and about 750 loops 32 per square inch of
the fabric 10.
Another embodiment of a method of making the compressible resilient
fabric 10 and/or devices 50 can include pile knitting. In a pile
knitted construction, the pile (for example, loops 32) stand out
substantially at right angles 42 from the technical back of the
knitted ground layer 20. As used herein, "pile" refers to yarns
(for example, loops 32) that stand away, or extend outwardly 42,
from the surface of the fabric 10. Sinker loops or underlaps can be
used to produce this effect. Such a technique can be varied by
using a double needle bar knitting machine, and pressing off on the
second set of needles to produce the pile surface layer. Point or
looped pile can be produced on a double-bar raschel knitting
machine by replacing the front bar needles by a point or pin bar
around which the pile yarns are overlapped. Pile knitting can
produce a high pile fabric that has resistance to unraveling
similar to the ravel-resistance achievable with warp knitting. A
pile knitting machine also has the ability to hold slack in a
stitch to create the ground layer 20 having higher tension than the
loops 32, thereby further enhancing the stability of the extended
loops 32. Pile knitting can provide for variation in the size of
the loops 32, which can be customized by changing the size of the
knitting elements.
Knitted constructions of the compressible resilient fabric 10 can
provide loops 32 having greater extensibility than in other
construction modalities, such as weaving. Enhanced loop
extensibility can allow greater height 43 of the loops 32 and thus
greater contact with a vessel wall and more surface area for blood
to clot between the exterior surface of a device 50 to which the
fabric 10 is attached and the interior wall of the vessel into
which the device 50 is implanted. Knitting also offers the
advantage of providing enhanced stretch and recovery, or
resiliency, of the loops 32. In addition, warp knitting can provide
a more flexible process for making a tubular device 50 with the
fabric 10, while still providing for the fabrication of the ground
layer 20 and the loop layer 30.
Although knitting may be a preferred technique for making some
embodiments of the compressible resilient fabric 10, the fabric 10
can also be made by weaving. Weaving may be utilized to produce a
high pile fabric having a highly stable ground layer 20. In
addition, a thinner and more flexible fabric 10 may be made by
weaving, which can facilitate production of a tubular device 50. In
woven embodiments of the fabric 10, the loops 32 can comprise
floated yarns. Thus, woven embodiments of the present invention may
provide the advantages of increased stability, while including a
thinner fabric 10.
Some embodiments of a method of making the compressible fabric 10
and/or intraluminal sealing member 52 can further include washing
the fabric 10 or sealing member 52 in about 90 degree C. water.
Washing the fabric 10 or sealing member 52 after formation can
advantageously cause some shrinkage of the fabric 10 or sealing
member 52. It may be desirable to place the fabric 10 or sealing
member 52 inside a protective housing such as a mesh covering or
bag to protect the loops 32 from rigorous agitation or disturbance
during washing. The wash can include use of detergent(s),
softener(s), and/or other additives.
After washing, the fabric 10 or sealing member 52 can be dried at
about 60-65 degrees C. The fabric 10 or sealing member 52 can be
dried in a tumble dryer. Drying at this temperature can cause the
fabric 10 or sealing member 52 to shrink further. The ground layer
20 and the loop layer 30 can each be knit with a yarn(s) having a
different degree of shrinkability. For example, the ground layer
yarn can be substantially more shrinkable than the loop layer yarn
31. In one particular embodiment, washing and drying the fabric 10
and/or intraluminal sealing member 52 can shrink the ground layer
20 about 40-60% and shrink the loop layer 30 about 7-8%.
After the washing and drying processes, the fabric 10 or sealing
member 52 can be thermoset in a dry oven. Such heat-setting can
improve the memory of the fibers in at least the loop layer yarns
31. In addition, heat-setting can create pockets in the ground
layer 20 that allow the loops 32 to be compressed into areas within
the ground layer 20, resulting in a thinner fabric in the
compressed configuration 41.
Certain embodiments of a method of making the fabric 10 or sealing
member 52 can further include stretching the fabric 10 or sealing
member 52 in the width or course-wise direction prior to drying the
fabric 10 or sealing member 52 so as to heat set the fabric 10 or
sealing member 52 under tension. For example, in some embodiments,
each of the yarn ends of the fabric 10 or sealing member 52 can be
releasably attached to pins in a pin frame. The pins in the pin
frame can secure the edges of the fabric 10 or sealing member 52 to
stabilize the fabric 10 or sealing member 52 with an even tension
throughout the fabric 10 or sealing member 52 in order to achieve a
consistent degree of final shrinkage as the fabric 10 or sealing
member 52 is being heat set. Stretching the fabric 10 or sealing
member 52 in the heat-setting process can thus provide a desired
orientation for memory by the fabric 10 or sealing member 52 once
heat set.
Some embodiments of the present invention can include a method of
using the compressible resilient fabric 10 and/or devices 50
including the compressible resilient fabric 10 as described herein.
For example, one such a method can include utilizing the device 50
comprising the substantially tubular inner member 51, such as the
stent 53, and the intraluminal sealing member 52 attachable to the
exterior of the inner member 51. The sealing member 52 can include
the ground layer 20 of knitted yarn and the loop layer 30
comprising a plurality of loops 32 of yarn 31, each loop 32 having
a point 33 knit into the ground layer 20. The sealing member 52 can
be compressed from the non-compressed configuration 40, in which
each loop 32 has an apex 34 extending substantially perpendicularly
and radially outward 42 from the ground layer 20, into the
compressed configuration 41, in which each loop 32 is collapsed
onto the ground layer 20. After the device 50 is implanted into a
lumen in a human or animal body and compression is relieved, the
sealing member 52 can recover so as to substantially resume its
non-compressed configuration 40. The intraluminal sealing member 52
can be adapted to promote sealing between the inner member 51 and a
lumen wall.
Although the present invention has been described with reference to
particular embodiments, it should be recognized that these
embodiments are merely illustrative of the principles of the
present invention. Those of ordinary skill in the art will
appreciate that a compressible resilient fabric 10, device 50,
system, kit, and methods of the present invention may be
constructed and implemented in other ways and embodiments.
Accordingly, the description herein should not be read as limiting
the present invention, as other embodiments also fall within the
scope of the present invention.
* * * * *